Catalyst for bulk polymerization

ABSTRACT

A catalyst for bulk polymerization comprising an organometallic compound represented by specified formula and a thiol is provided. The specified organometallic compound is a metallocene compound such as titanocene or zirconocene. The use of this bulk polymerization catalyst comprising a metallocene compound and a thiol enables stable bulk polymerization of a polymerizable unsaturated compound such as an acrylic monomer, the reaction control of which has been difficult in the bulk polymerization of the prior art.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.09/540,571 filed Mar. 31, 2000 now Pat. No. 6,489,412.

FIELD OF THE INVENTION

The present invention relates to a novel catalyst for bulkpolymerization and a polymerization method using the bulk polymerizationcatalyst.

BACKGROUND OF THE INVENTION

Polymerizable compounds having polymerizable double bonds such asacrylic acid, methacrylic acid, styrene and derivatives thereof can bepolymerized, in the presence of an initiator of a radicalpolymerization, by the conventional emulsion polymerization process,suspension polymerization process, solution polymerization process orbulk polymerization process. The thus obtained polymers find applicationin various uses such as moldings, pressure sensitive adhesives, paintsand fibers. Of these polymers, polymers produced by the emulsionpolymerization process, suspension polymerization process and solutionpolymerization process have advantages in that, because thepolymerization is carried out in a reaction solvent or dispersionmedium, the polymerization temperature can be easily controlled, and thereaction solution has fluidity even if the rate of polymerization ishigh.

However, the polymers produced by the emulsion polymerization process,suspension polymerization process and solution polymerization process,according to uses, must be subjected to operations such asprecipitation, filtration, washing and drying for separating theproduced polymer from the reaction solvent or dispersion medium. Thiscauses the process to be laborious and time-consuming.

By contrast, the bulk polymerization process is a process in which thepolymerization is carried out in the absence of a solvent or adispersion medium. Therefore, in the bulk polymerization process, it isnot needed to add an organic solvent, a dispersant, an emulsifier andthe like. The reaction system of the bulk polymerization can be simplebecause no impurities such as an organic solvent which participates inthe polymerization are contained therein, and the obtained polymer isfree from the contaminating of an emulsifier, a dispersant and otherimpurities therein. Furthermore, it is not needed to remove a solvent ordispersion medium for the purpose of obtaining the desired polymer. Fromthese viewpoints, the bulk polymerization process is an industriallyadvantageous process.

However, the velocity of polymerization reaction is generally extremelyhigh in the bulk polymerization process, and practically it is extremelydifficult to control the bulk polymerization process. In polymers formedat high temperatures with the failure to control the polymerizationvelocity, it is likely that molecular terminals become unstable due todisproportionation termination, that the molecular weight is lowered,and that branching or gelation of the polymer occurs by, for example,hydrogen abstraction from the previously formed polymer. Therefore, itbecomes difficult to implement not only a molecular design regarding themolecular weight, molecular weight distribution, etc. of polymer butalso a definite design of molecular structure because of the polymerbranching and formation of disproportionation termination terminals.Furthermore, in polymers formed at high temperatures with the failure tocontrol the polymerization velocity, gels may be formed rapidly in alarge amount, so that, in the worst case, there is even the danger ofexplosion attributed to runaway reaction.

Nevertheless, the velocity of polymerization of, for example, styreneand methyl methacrylate is relatively low, so that, even in the bulkpolymerization, the reaction control thereof can be managed. Thus, thecontrolling method has been investigated for long. In the bulkpolymerization of styrene, methyl methacrylate or the like, mercaptansmay be used for controlling the molecular weight and molecular weightdistribution thereof.

However, in the bulk polymerization reaction using mercaptans, it isoften difficult to effect a homogeneous reaction control and the typesof monomers subjected to the bulk polymerization are limited.

Apart from the above, in the polymerization reaction, the catalyst isvaried depending on the type of employed monomer. For example,metallocene compounds such as titanocene are used as the catalyst forpolymerization of ethylene or the like. However, the use of metallocenecompounds as the catalyst for polymerization of monomers other thanα-olefins is little known except for the use thereof together with asensitizer in photopolymerization. Japanese Patent Laid-open PublicationNo. 9(1997)-5996 discloses an invention of photopolymerizablecomposition containing a compound having at least one ethylenicallyunsaturated double bond capable of addition polymerization, a titanocenecompound as a photopolymerization initiator, a sensitizer capable ofsensitizing the titanocene compound, the photopolymerization compositionfurther containing a heterocyclic thiol compound. In the inventiondisclosed in the publication, the titanocene compound is used as aphotopolymerization catalyst, and, in the publication, there is nodescription regarding the use of titanocene compounds as a catalyst forbulk polymerization. Further, the heterocyclic thiol compound describedin the publication is a visible radiation sensitizer.

Generally, in the reaction used in metallocene compounds such astitanocene compounds as a catalyst, a sulfurous or sulfuric compound isa compound which lowers the catalytic activity of metallocene compounds.The above-mentioned use of a sulfurous or sulfuric compound as acompound capable of exerting specified function and effect like theabove visible radiation sensitizer signifies a highly exceptional usagein metallocene compounds employed as a catalyst. That is, generally, asulfurous or sulfuric compound is a catalyst poison to metallocenecompounds used as a catalyst. Therefore, the addition of a sulfurous orsulfuric compound to a reaction system containing a metallocene compoundas a catalyst constitutes a regularly inconceivable combination.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a novel catalyst foruse in bulk polymerization. It is a particular object of the presentinvention to provide a novel catalyst capable of performing a bulkpolymerization of a monomer having a polymerizable unsaturated bond,such as an acrylic monomer, without runaway of reaction.

It is another object of the present invention to provide a novel methodof bulk polymerization in which use is made of the above novel catalyst.

SUMMARY OF THE INVENTION

The catalyst for bulk polymerization according to the present inventioncomprises an organometallic compound, which is represented by theformula (I), and a thiol:

wherein M represents a metal selected from the group consisting ofmetals of Groups 4A, 4B, 5A and 5B of the periodic table, chromium,ruthenium and palladium; each of R¹ and R² independently represents atleast one group selected from the group consisting of an unsubstitutedor substituted aliphatic hydrocarbon group, an unsubstituted orsubstituted alicyclic hydrocarbon group, an unsubstituted or substitutedaromatic hydrocarbon group and an unsubstituted or substituted siliconcontaining group, a hydrogen atom or a single bond, provided that R¹ andR² may cooperate with each other to bond the two 5-membered rings shownin the formula and provided that neighboring groups of R¹ or R² maycooperate with each other to form a cyclic structure;

-   -   each of a and b independently is an integer of 1 to 4; X        represents a halogen atom or a hydrocarbon group optionally        having at least one hydrogen atom thereof substituted with a        halogen atom; and n is 0 or an integer substracting 2 from        valence of metal M.

The polymerization method of the present invention comprises conductinga bulk polymerization of a monomer having a polymerizable unsaturatedbond in the presence of the above catalyst for bulk polymerizationcomprising an organometallic compound represented by the above formula(I) and a thiol.

The inventors have conducted investigations into the bulk polymerizationof acrylic monomers. As a result, it has been found that a catalystcomprising a combination of a metallocene compound and a thiol exerts asurprisingly high catalytic activity in the bulk polymerization ofacrylic monomers, which has been difficult in the prior art. The presentinvention has been completed on the basis of this finding.

The use of the bulk polymerization catalyst comprising an organometalliccompound represented by the above formula (I) and a thiol according tothe present invention enables conducting a stable bulk polymerization ofa monomer having a polymerizable unsaturated bond, such as an acrylicmonomer.

DETAILED DESCRIPTION OF THE INVENTION

The bulk polymerization catalyst of the present invention andpolymerization method in which use is made of this bulk polymerizationcatalyst will be described in detail below.

The catalyst of the present invention can subject a compound having apolymerizable unsaturated bond to conduct a stable bulk polymerization.

The organometallic compound for use in the bulk polymerization catalystof the present invention is represented by the formula (I):

In the formula (I), M represents a metal selected from the groupconsisting of metals of Groups 4A, 4B, 5A and 5B of the periodic table,chromium, ruthenium and palladium. The metal M is, for example,titanium, zirconium, chromium, ruthenium, vanadium, palladium or tin.

In the formula (I), each of R¹ and R² independently represents at leastone group selected from the group consisting of:

an unsubstituted or substituted aliphatic hydrocarbon group,

an unsubstituted or substituted alicyclic hydrocarbon group,

an unsubstituted or substituted aromatic hydrocarbon group, and

an unsubstituted or substituted silicon containing group, or

a hydrogen atom or a single bond.

Provided, however, that R¹ and R² may cooperate with each other to bondthe two 5-membered rings shown in the formula and that neighboringgroups of R¹ or R² may cooperate with each other to form a cyclicstructure.

Further, in the formula (I), each of a and b independently is an integerof 1 to 4.

X represents a halogen atom such as chlorine, bromine or iodine, or ahydrocarbon group optionally having at least one hydrogen atom thereofsubstituted with a halogen atom.

n is 0 or an integer subtracting 2 from valence of metal M.

Examples of the above organometallic compounds include:

titanocene compounds such as dichloro(dicyclopentadienyl)titanium,bisphenyl(dicyclopentadienyl)titanium,bis-2,3,4,5,6-pentafluorophen-1-yl(dicyclopentadienyl)titanium,bis-2,3,5,6-tetrafluorophen-1-yl(dicyclopentadienyl)titanium,bis-2,5,6-trifluorophen-1-yl(dicyclopentadienyl)titanium,bis-2,6-difluorophen-1-yl(dicyclopentadienyl)titanium,bis-2,4-difluorophen-1-yl(dicyclopentadienyl)titanium,bis-2,3,4,5,6-pentafluorophen-1-yl(dimethylcyclopentadienyl)titanium,bis-2,3,5,6-tetrafluorophen-1-yl(dimethylcyclopentadienyl)titanium,bis-2,6-difluorophen-1-yl(dimethylcyclopentadienyl)titanium andbis-2,6-difluoro-3-(pyr-1-yl)phen-1-yl(dimethylcyclopentadienyl)titanium;

zirconocene compounds such as dichloro(dicyclopentadienyl)zirconium,bisphenyl(dicyclopentadienyl)zirconium,bis-2,3,4,5,6-pentafluorophen-1-yl(dicyclopentadienyl)zirconium,bis-2,3,5,6-tetrafluorophen-1-yl(dicyclopentadienyl)zirconium,bis-2,5,6-trifluorophen-1-yl(dicyclopentadienyl)zirconium,bis-2,6-difluorophen-1-yl(dicyclopentadienyl)zirconium,bis-2,4-difluorophen-1-yl(dicyclopentadienyl)zirconium,bis-2,3,4,5,6-pentafluorophen-1-yl(dimethylcyclopentadienyl)zirconium,bis-2,3,5,6-tetrafluorophen-1-yl(dimethylcyclopentadienyl)zirconium,bis-2,6-difluorophen-1-yl(dimethylcyclopentadienyl)zirconium andbis-2,6-difluoro-3-(pyr-1-yl)phen-1-yl(dimethylcyclopentadienyl)zirconium;

chloro(dicyclopentadienyl)vanadium,chloro(bismethylcyclopentadienyl)vanadium,chloro(bispentamethylcyclopentadienyl)vanadium,chloro(dicyclopentadienyl)ruthenium andchloro(dicyclopentadienyl)chromium. These organometallic compounds canbe used either individually or in combination.

These organometallic compounds can be used in a regularly employedcatalyst amount. These organometallic compounds are generally used in anamount of, for example, 1 to 0.001 part by weight, preferably 0.01 to0.005 part by weight, per 100 parts by weight of polymerizableunsaturated compound to be polymerized.

Examples of the thiols for use in the present invention include:

alkylthiols having no functional group other than a thiol group, such asethylmercaptan, butylmercaptan, hexylmercaptan, tert-dodecylmercaptan,n-dodecylmercaptan and octylmercaptan,

aromatic thiols having no functional group other than a thiol group,such as phenylmercaptan and benzylmercaptan,

thiols having a functional group other than a thiol group, such asβ-mercaptopropionic acid, mercaptoethanol,3-mercaptopropyl(trimethoxy)silane and thiophenol,

polyfunctional thiol compounds obtained by esterifying trithioglycerolor pentaerythritol with β-mercaptopropionic acid, and

polymeric thiols having an active thiol group, such as polysulfidepolymers.

The addition amount (use amount) of the above thiols can appropriatelybe determined taking the properties of polymer intended to obtain intoaccount. That is, when the thiol concentration in a reaction system isincreased, not only the conversion of monomers per time but also thefinal (reached) conversion (ratio of polymer converted from monomer tomonomer) becomes high. On the other hand, the increase of theorganometallic compound leads to an increase of the conversion per timebut does not exert any marked influence on the final conversion.Although the addition amount of organometallic compound does not exertany significant influence on the molecular weight of obtained polymer,the reaction does not advance when the organometallic compound is notused. Further, when the addition amount of the thiol is increased, thepolymerization velocity becomes higher. From these trends, it is assumedthat, in the catalyst of the present invention, the organometalliccompound exerts an activating catalytic function while the thiol exertsa polymerization initiating function (namely, functions as apolymerization initiating species) throughout the reaction. Thus, in thecatalyst of the present invention, the addition amount of thiol isconsidered to exert a large influence on the molecular weight and theconversion.

Therefore, although the addition amount of thiols can appropriately bedetermined taking into account the molecular weight of polymer intendedto obtain, the polymerization velocity, etc., the organometalliccompound and the thiol are generally used in a molar ratio of 100:1 to1:50,000, preferably 10:1 to 1:10,000, for realizing a smooth reactionadvance without runaway of reaction.

The whole amount of thiol can be added to the reaction system at theinitiation of the reaction. Also, the thiol can be added in such amanner that part of the thiol is added at the initiation of thereaction, the reaction is conducted for a desirable period of time andthereafter the rest of thiol is further added optionally together with apolymerizable unsaturated compound. The conversion is increased by theabove further addition of thiol, or thiol together with a polymerizableunsaturated compound.

In the bulk polymerization catalyst of the present invention, disulfide,trisulfide and tetrasulfide compounds can be used in addition to theabove organometallic compound and thiol as a polymerization initiatingcatalyst for the purpose of regulating the polymerization velocity andpolymerization degree.

Examples of the disulfide, trisulfide and tetrasulfide compounds as apolymerization regulator usable in the present invention include diethyltrisulfide, dibutyl tetrasulfide, diphenyl disulfide,bis(2-hydroxyethyl) disulfide, bis(4-hydroxybutyl) tetrasulfide,bis(3-hydroxypropyl) trisulfide, bis(3-carboxypropyl) trisulfide,bis(3-carboxypropyl) tetrasulfide, bis(3-propyltrimethoxysilane)disulfide and bis(3-propyltriethoxysilane) trisulfide. These sulfidecompounds can be used either individually or in combination. Thesesulfide compounds can be used in such an amount that the polymerizationcatalyst is not deactivated in the bulk polymerization of the presentinvention. For example, the sulfide compounds are generally used in anamount of 50 to 0 part by weight, preferably 20 to 0.005 part by weight,per 100 parts by weight of polymerizable unsaturated compound to bepolymerized.

The bulk polymerization of a polymerizable unsaturated compound can becarried out with the use of the bulk polymerization catalyst comprisingthe organometal and the thiol according to the present invention.

For example, polymerizable unsaturated compounds represented by thefollowing formulae (B), (B-1) and (B-2) are preferably used as thepolymerizable unsaturated compound subjected to the bulk polymerizationusing the catalyst of the present invention.

In the formula (B), each of R⁷ to R⁹ independently represents a hydrogenatom, a halogen atom or an alkyl group having 1 to 3 carbon atoms. R¹⁰represents a hydrogen atom, an alkali metal atom or a hydrocarbon grouphaving 1 to 22 carbon atoms (the hydrocarbon group may be linear or mayhave side chains; the hydrogen atoms of the hydrocarbon group or groupconstituting the side chains may partially be substituted with at leastone polar group, halogen atom or reactive functional group selected fromthe group consisting of —OH, —F, —COOH, —Cl, —NH₂, —Si(OH₃)₃,—Si(OCH₃)₂(CH₃) and —Si(CH₃)₂(OCH₃); and the hydrocarbon group may havea double bond or may have a cyclic structure). Specifically, R¹⁰ can be,for example, an alkyl group, a cycloalkyl group, an aryl group, analkenyl group, a cycloalkenyl group, an alkoxy group or an alkyl ethergroup. The hydrogen atoms of the group R¹⁰ may partially be substitutedwith a halogen atom, a sulfonic acid residue, a glycidyl group or thelike.

In the formula (B-1), R¹¹ to R¹³ have the same meaning as the above R⁷to R⁹. R¹⁴ represents any of hydroxyl, —CO—NH₂, —CN, glycidyl, alkyl,alkoxy, alkenyl, cycloalkenyl, aryl, allyl ether, alkyl ether,alkoxysilyl, silanol and halogenated silyl groups. The hydrogen atoms ofthe group R¹⁴ may at least partially be substituted with a halogen atom,etc. Moreover, the group R¹⁴ may be a group which contains a structuralunit derived from an alkylene glycol, an alkoxysilyl group, analkylalkoxysilyl group, a methylol group or an alkoxyamido group.

In the formula (B-2), R¹⁵ and R¹⁷ have the same meaning as the above R⁷to R⁹. Each of R¹⁶ and R¹⁸ independently represents any of carboxyl,hydroxyl, —CO—NH₂, —CN, glycidyl, alkyl, alkoxy, alkenyl, cycloalkenyland aryl groups. The hydrogen atoms of the groups R¹⁶ and R¹⁸ may atleast partially be substituted with a halogen atom, etc. Moreover, thesegroups R¹⁶ and R¹⁸ may cooperate with two carbon atoms bonded withgroups R¹⁵ and R¹⁷ to form a cyclic structure. The cyclic structure mayhave a double bond.

Furthermore, particular examples of these polymerizable unsaturatedcompounds include:

acrylic acid and salts thereof such as alkali metal acrylates;

methacrylic acid and salts thereof such as alkali metal methacrylates;

alkyl esters of acrylic acid such as methyl acrylate, ethyl acrylate,propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate,2-ethylhexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylateand dodecyl acrylate;

aryl esters of acrylic acid such as phenyl acrylate and benzyl acrylate;

alkoxyalkyl acrylates such as methoxyethyl acrylate, ethoxyethylacrylate, propoxyethyl acrylate, butoxyethyl acrylate and ethoxypropylacrylate;

alkyl esters of methacrylic acid such as methyl methacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate, pentylmethacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octylmethacrylate, nonyl methacrylate, decyl methacrylate and dodecylmethacrylate;

aryl esters of methacrylic acid such as phenyl methacrylate and benzylmethacrylate;

alkoxyalkyl methacrylates such as methoxyethyl methacrylate, ethoxyethylmethacrylate, propoxyethyl methacrylate, butoxyethyl methacrylate andethoxypropyl methacrylate;

(poly)alkylene glycol diacrylates such as ethylene glycol diacrylate,diethylene glycol diacrylate, triethylene glycol diacrylate,polyethylene glycol diacrylate, propylene glycol diacrylate, dipropyleneglycol diacrylate and tripropylene glycol diacrylate;

(poly)alkylene glycol dimethacrylates such as ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, triethylene glycoldimethacrylate, polyethylene glycol dimethacrylate, propylene glycoldimethacrylate, dipropylene glycol dimethacrylate and tripropyleneglycol dimethacrylate;

polyacrylates such as trimethylolpropane triacrylate;

polymethacrylates such as trimethylolpropane trimethacrylate;

acrylonitrile, methacrylonitrile and vinyl acetate;

vinyl halide compounds such as vinylidene chloride, 2-chloroethylacrylate and 2-chloroethyl methacrylate;

acrylic acid esters of alicyclic alcohol such as cyclohexyl acrylate;

methacrylic acid esters of alicyclic alcohol such as cyclohexylmethacrylate;

polymerizable compounds containing an oxazoline group such as2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline and2-isopropenyl-2-oxazoline;

polymerizable compounds containing an aziridine group such asacryloylaziridine, methacryloylaziridine, 2-aziridinylethyl acrylate and2-aziridinylethyl methacrylate;

vinyl monomers containing an epoxy group such as allyl glycidyl ether,glycidyl ether acrylate, glycidyl ether methacrylate, 2-ethylglycidylether acrylate and 2-ethylglycidyl ether methacrylate;

vinyl compounds containing a hydroxyl group such as 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,monoesters of acrylic acid or methacrylic acid and polypropylene glycolor polyethylene glycol and adducts of lactons and 2-hydroxyethyl(meth)acrylate;

fluorinated vinyl monomers such as fluorinated alkyl methacrylates andfluorinated alkyl acrylates;

unsaturated carboxylic acids other than (meth)acrylic acid such asitaconic acid, crotonic acid, maleic acid and fumaric acid, and salts,(partial) ester compounds and anhydrides of such unsaturated carboxylicacids;

vinyl monomers containing a reactive halogen such as 2-chloroethyl vinylether and vinyl monochloroacetate;

vinyl monomers containing an amido group such as methacrylamide,N-methylolmethacrylamide, N-methoxyethylmethacrylamide andN-butoxymethacrylamide;

vinyl compound monomers containing an organosilicon group such asvinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane,allyltrimethoxysilane, trimethoxysilylpropylallylamine and2-methoxyethoxytrimethoxysilane; and

diene compounds such as ethylidenenorbornene, isoprene, pentadiene,vinylcyclohexene, chloroprene, butadiene, methylbutadiene,cyclobutadiene and methylbutadiene.

Moreover, macromonomers (e.g., fluoromonomers, silicon containingmonomers, macromonomers, styrene, silicone, etc.) having a radicalpolymerizable vinyl group at an end of vinyl-polymerized monomer can bementioned as further examples of the polymerizable unsaturatedcompounds.

These polymerizable unsaturated compounds can be used eitherindividually or in combination. Although these polymerizable unsaturatedcompounds may be liquid, or solid, or gaseous, it is preferred from theeasiness of operation that a liquid monomer be used at the reactiondepending on reaction conditions.

Stable bulk polymerization of these polymerizable unsaturated compoundscan be accomplished by the use of the catalyst for bulk polymerizationaccording to the present invention comprising the organometalliccompound of the formula [I] and the thiol.

The term of “bulk polymerization” used herein means a reaction in whicha polymerizable unsaturated compound is polymerized substantially in theabsence of any solvent. Thus, generally, the reaction system of bulkpolymerization does not contain any reaction solvent. The expression“substantially in the absence of any solvent” means that any reactionsolvent is not used and should not be construed as excluding anextremely small amount of solvent for dissolution or for dispersionemployed to homogeneously disperse the catalyst for the bulkpolymerization according to the present invention comprising theorganometallic compound of the formula (I) and the thiol in the entiretyof monomer, solvents remaining in raw materials, etc.

This bulk polymerization reaction is generally carried out in anatmosphere of inert gas. Thus, active gases such as oxygen are notpresent in the reaction system of bulk polymerization. Nitrogen, argon,helium and carbon dioxide gases can be mentioned as the inert gas foruse in bulk polymerization.

Although the bulk polymerization catalyst of the present inventioncomprising the organometallic compound of the formula (I) and the thiolcan be used in a regularly employed catalyst amount in this bulkpolymerization, the organometallic compound of the formula (I) isgenerally added in an amount of 0.0000001 to 0.0001 mol per mol ofunsaturated group of the polymerizable unsaturated compound, andpreferably in such an amount that the molar ratio of organometalliccompound to thiol is in the range of 10:1 to 1:10,000 in accordance withthe molar amount of added thiol. The thiol is generally used in anamount of 0.00001 to 0.7 mol, preferably 0.0001 to 0.5 mol.

Although the bulk polymerization reaction using the catalyst of thepresent invention can be performed in heated or warm atmosphere or whilecooling the reaction system, depending on the type of polymerizableunsaturated compound, it is preferred that the reaction temperature forbulk polymerization be set at 0 to 150° C., especially 25 to 120° C. Thebulk polymerization reaction can be stably advanced without runaway bysetting the reaction temperature for bulk polymerization so as to fallwithin the above range. Even if an acrylic-ester-type polymerizableunsaturated compound of relatively high polymerizability is employed,although depending on the activity of the unsaturated group of theemployed polymerizable unsaturated compound, setting the reactiontemperature at 0° C. or below causes lowering of the catalyticactivities of the organometallic compound of the formula (I) and thioland therefore the time required for attaining a satisfactory conversionis prolonged and not efficient. Further, even if a compound of lowpolymerization activity such as a styrene-type unsaturated compound isemployed, a satisfactory polymerization rate can be attained by settingthe reaction temperature at 25° C. or higher.

Setting the reaction temperature at 150° C. or higher may invite thedanger of runaway of reaction attributed to extreme heat generationduring the polymerization reaction. The smooth advance of reaction canbe maintained without runaway of reaction by setting the polymerizationtemperature at 120° C. or below.

Although the reaction time can be appropriately set taking into accountthe conversion, molecular weight, etc. in the bulk polymerization of thepresent invention, it is generally preferred, for example, under theabove conditions, that the reaction time be set at 2 to 12 hr,especially 2 to 8 hr.

This bulk polymerization reaction can be terminated by lowering thetemperature of the reaction mixture or preferably by adding apolymerization inhibitor such as benzoquinone.

Polymers of a polymerization rate of generally at least 40%, preferablyat least 60%, can be obtained by performing the bulk polymerization inthe above described manner. Unreacted monomers, residual thiol and otherlow-boiling-point compounds remaining in the reaction system can beremoved with the use of, for example, an evaporator in vacuum. Theheating residue at 150° C. of the thus obtained polymer is generally atleast 90%, preferably at least 95%.

With respect to the thus obtained polymer, the weight average molecularweight (Mw) measured by gel permeation chromatography (GPC) is generallyin the range of 500 to 1,000,000, preferably 1000 to 300,000, while thenumber average molecular weight (Mn) is generally in the range of 500 to1,000,000, preferably 1000 to 100,000. The dispersion index thereof(Mw/Mn) is generally in the range of 1.02 to 9.0, preferably 1.2 to 3.0.

The thus obtained polymer is mostly a generally viscous liquid. Theviscosity measured at 23° C. is generally in the range of 100 to1,000,000 centipoises (cps), preferably 1000 to 100,000 centipoises(cps).

Unless a deliming treatment which removes the deactivated catalyst fromthe obtained polymer is conducted, the organometallic compound is mixedin the polymer obtained by polymerization with the use of the catalystfor bulk polymerization according to the present invention. Further,sulfurous or sulfuric groups derived from the added thiol are bonded toat least a part of molecular terminals of the obtained polymer. In thisconnection, although the compound having a thiol group is used as apolymerization initiating species in the bulk polymerization with thecatalyst according to the present invention, commonly such a thiolcompound alone exhibits no activity as polymerization initiatingspecies. When an organometallic compound is used in accordance with thepresent invention, however, a thiol group derivable from the thiolcompound is converted to an active species capable of initiatingpolymerization by the organometallic catalyst to thereby become aninitiating species for the monomer. Therefore, in this reaction, theconversion per time is enhanced by an increase of the amount of thiolrelative to the amount of monomer. Accordingly, sulfurous or sulfuricgroups derived from the added thiol are bonded to polymerizationinitiation terminals of the obtained polymer. However, the added thiolfunctions not only as a polymerization initiating species but also as achain transfer agent, so that the molecular weight (degree ofpolymerization) and conversion of monomer are greatly influenced by theamount of thiol. It can be presumed from these phenomena that theadvance and termination of polymerization in this reaction are those ofradical polymerization. The thio-radical (•S) of the thiol havingundergone a hydrogen abstraction by the chain transfer once more attacksthe monomer as a polymerization initiating species. Therefore, sulfurousor sulfuric groups derived from the added thiol are bonded to terminalsof the polymer produced by this polymerization method, irrespective ofthe addition amount of thiol.

With respect to the reaction system of the present invention, the samereaction as in the above bulk polymerization can be effected in a polarorganic solvent such as an alcohol or a dispersion medium such as water.Therefore, it is conceivable that a radical reaction is predominant inthe polymerization of the present invention. Accordingly, it can bepresumed that the reaction termination ends of obtained polymer consistof hydrogen attributed to the chain transfer from the thiol, or thethiol having thio-radicals due to the conversion to radical, andsulfurous or sulfuric groups derived from the thiol by radical couplingwith growing polymer radicals.

In the obtained polymer, the organometallic compound remains in itsoriginal form (that is, the organometallic compound), or in the form ofbeing bonded with another organic group, or in the form of a metal. Thethiol directly contributes to the polymer forming reaction and thereaction is advanced while the thiol itself is being decomposed, so thatterminal groups derived from the thiol are introduced in the polymerends.

The above presumption and advance of reaction are believed to be themost rational by the inventor on the basis of various phenomenaexperienced in the reaction of the present invention, which naturally inno way limit the scope of the present invention.

The polymer obtained by the method of the present invention is generallya viscous liquid, which is however cured by reaction in the presence ofcompounded curing agent or the like. The resultant curing product haselasticity.

The polymer obtained by the method of the present invention can beapplied to uses in which the curability thereof is utilized, uses inwhich the elasticity of the cured product is utilized, uses in which thepolymer being a viscous liquid is utilized and other uses. For example,the polymer obtained by the method of the present invention can be usedin coating materials (paint), sealing materials, coating filmwaterproofers, pressure sensitive adhesives, adhesives, sheeted items(gas permeable sheets, protective sheets, water barrier sheets, dampingsheets, transfer sheets, light controlling sheets, antistatic sheets,conductive sheets, curing sheets, noise insulating sheets, shade sheets,decorative sheets, marking sheets and flame retardant sheets) and rawmaterials thereof, film moldings (marking films, protective films, inkfixing films and laminate films) and raw materials thereof, foams (hard,soft, semirigid and flame retardant) and raw materials thereof, inkvehicles, reactive plasticizers, plasticizers, diluents,compatibilizers, intermediate materials for resins such as polyesterresins, polyurethane resins, polycarbonate resins and various blockpolymers, reforming materials, additives, fiber modifiers, fiber surfacetreatments, paper processing agents, paper modifiers, surfactants,dispersion stabilizers, dispersion mediums, solvents, viscosityregulators, adsorbents, hair treatments, toner additives,electrification controlling agents, antistatic agents, low-shrinkageagents, antifogging agents, stainproofing agents, hydrophilicityimparting agents, lipophilicity imparting agents, medicine carriers,carriers for agricultural chemicals, cosmetic compounding agents,lubricants, polymer alloy additives, gel coating agents, FRP resins, FRPresin additives, resins for artificial marble, resin additives forartificial marble, casting resins, raw materials for UV/EV cured resins,tackifiers, various binders (magnetic recording medium, for molding, forburned products and glass fiber sizing material), RIM urethanemodifiers, resins for glass laminate, damping materials, noiseinsulating materials, resins for separating membranes, soundproofingmaterials, sound absorbing materials, artificial leathers, artificialskins, synthetic leathers, various industrial parts, daily needs, moldeditems for toiletry, acrylic urethane rubbers, acrylic urethane rubbermodifiers, acrylic urethane foam modifiers, urethane rubber modifiers,urethane foam plasticizers, urethane foam modifiers and acrylic rubbermodifiers.

EFFECT OF THE INVENTION

The use of the catalyst of the present invention enables performing astable bulk polymerization, without runaway of reaction, even ifpolymerizable unsaturated compounds such as acrylic monomers haveexperienced relative difficulty in controlling the polymerizationreaction.

Further, the properties of obtained polymer and polymerization conditiontherefor, such as polymerization rate, molecular weight andpolymerization velocity, can be controlled mainly by regulating theaddition amount of thiol with the use of the catalyst of the presentinvention.

Moreover, groups derived from the thiol are introduced in molecularterminals of the polymer produced with the use of the catalyst of thepresent invention, so that the employed thiol compound can securely beintroduced in at least one end of each polymer molecule. When theemployed thiol has a functional group other than the thiol group, thefunctional group can be introduced in at least one end of each obtainedpolymer molecule. A curing reaction and various other reactions can beperformed by utilizing the introduced functional group.

EXAMPLES

The present invention will further be illustrated below with referenceto the following Examples which in no way limit the scope of theinvention.

Example 1

100 parts by weight of ethyl acrylate and 0.05 part by weight ofruthenocene as a metal catalyst were charged into a flask equipped withan agitator, a nitrogen gas introduction tube, a thermometer and areflux cooling tube. The flask contents were heated to 70° C. whileintroducing nitrogen gas into the flask.

Subsequently, 6 parts by weight of β-mercaptopropionic acidsatisfactorily purged with nitrogen gas was added to the flask contentsunder agitation. Cooling and heating were performed for two hours afterthe addition of the β-mercaptopropionic acid so that the temperature ofthe flask contents under agitation was maintained at 70° C. Further,another 6 parts by weight of β-mercaptopropionic acid satisfactorilypurged with nitrogen gas was added to the flask contents underagitation. Reaction was carried out for four hours after the furtheraddition of the β-mercaptopropionic acid with further cooling andheating so that the temperature of the flask contents under agitationwas maintained at 70° C.

After the above reaction performed for 6 hr in total, the reactionproduct was cooled to room temperature. Then, 20 parts by weight of abenzoquinone solution (95% THE solution) was added to the reactionproduct to thereby terminate polymerization.

With respect to the thus obtained THF solution of reaction product, theratio of monomer residue was measured by gas chromatography, therebydetermining the polymerization rate thereof.

As a result, it was found that a reaction product whose conversion was78% was obtained. No runaway of polymerization reaction was observed atall during the polymerization.

Thereafter, the obtained reaction product was transferred into anevaporator and slowly heated up to 80° C. in vacuum to thereby removeTHF, monomer residue and thiol compound residue.

The 150° C. heating residue of the thus obtained polymer was 99.2%.

With respect to the obtained polymer, the molecular weight measured bygel permeation chromatography (GPC) was 4400 in terms of Mw and 2800 interms of Mn. The dispersion index was 1.6, and the viscosity at 23° C.was 48,500 centipoises (cps).

Example 2

100 parts by weight of methyl acrylate, 10 parts by weight oftrimethylolpropane triacrylate and 0.02 part by weight of zirconocenedichloride as a metal catalyst were charged into a flask equipped withan agitator, a nitrogen gas introduction tube, a thermometer and areflux cooling tube. The flask contents were gently heated to 80° C.while introducing nitrogen gas into the flask.

Subsequently, 50 parts by weight of 3-mercaptopropyl(trimethoxy)silanesatisfactorily purged with nitrogen gas was added to the flask contentsunder agitation. Reaction was carried out for eight hours after theaddition of the 3-mercaptopropyl(trimethoxy)silane while cooling andheating so that the temperature of the flask contents under agitationwas maintained at 80° C.

After the above reaction, the reaction product was cooled to roomtemperature. Then, 20 parts by weight of a benzoquinone solution (95%THF solution) was added to the reaction product to thereby terminatepolymerization.

With respect to the thus obtained THF solution of reaction product, theratio of monomer residue was measured by gas chromatography, therebydetermining the polymerization rate thereof.

As a result, it was found that the conversion was 82%. No runaway ofpolymerization reaction was observed at all during the abovepolymerization.

Thereafter, the obtained reaction product was transferred into anevaporator and slowly heated up to 80° C. in vacuum to thereby removeTHF, monomer residue and thiol compound residue.

The 150° C heating residue of the thus obtained polymer was 98.7%.

With respect to the obtained polymer, the molecular weight measured bygel permeation chromatography (GPC) was 1400 in terms of Mw and 800 interms of Mn. The dispersion index was 1.8, and the viscosity at 23° C.was 1300 centipoises (cps).

Example 3

80 parts by weight of styrene, 20 parts by weight ofperfluorooctylethylene and 0.1 part by weight of titanocene dichlorideas a metal catalyst were charged into a flask equipped with an agitator,a nitrogen gas introduction tube, a thermometer and a reflux coolingtube. The flask contents were heated to 80° C. while introducingnitrogen gas into the flask.

Subsequently, 10 parts by weight of 2-mercaptoethanol satisfactorilypurged with nitrogen gas was added to the flask contents underagitation. Reaction was carried out for two hours after the addition ofthe 2-mercaptoethanol while cooling and heating so that the temperatureof the flask contents under agitation was maintained at 80° C.

Thereafter, 10 parts by weight of 2-mercaptoethanol was added to theflask contents under agitation, and further reaction was performed fortwo hours. Moreover, 20 parts by weight of 2-mercaptoethanol was addedto the flask contents under agitation, and still further reaction wasperformed for four hours.

Upon the passage of 8 hr in total, the reaction product was cooled toroom temperature. Then, 20 parts by weight of a benzoquinone solution(95% THF solution) was added to the reaction product to therebyterminate polymerization.

With respect to the thus obtained THF solution of reaction product, theratio of monomer residue was measured by gas chromatography, therebydetermining the polymerization rate thereof.

As a result, it was found that the conversion was 68%. No runaway ofpolymerization reaction was observed at all during the abovepolymerization.

Comparative Example 1

Reaction was performed in the same manner as in Example 1, except thatthe metal catalyst ruthenocene was not added. With respect to the thusobtained polymer, the conversion was 9%.

Comparative Example 2

Reaction was performed in the same manner as in Example 1, except thatthe thiol compound β-mercaptopropionic acid was not added. With respectto the thus obtained polymer, the conversion was 1%.

1. A catalyst for bulk polymerization comprising an organametalliccompound and a thiol, said thiol being selected from the groupconsisting of: alkylthiols having no functional group other than a thiolgroup; aromatic thiols having no functional group other than a thiolgroup; thiols having a functional group other than a thiol groupselected from the group consisting of β-mercaptopropionic acid,mercaptoethanol, 3-mercaptopropyl (trimethoxy) silane and thiophenol;polyfunctional thiol compounds obtained by esterifying trithioglycerolor pentaerythritol with β-mercaptopropionic acid, and polmeric thiolshaving an active thiol group, said organometallic compound representedby the formula:

wherein M represents a metal selected from the group consisting ofmetals of Groups 4A, 4B, 5A and 5B of the periodic table, chromium,ruthenium and palladium; each of R¹ and R² independently represents atleast one group selected from the group consisting of an unsubstitutedor substituted aliphatic hydrocarbon group, an unsubstituted orsubstituted alicyclic hydrocarbon group, an unsubstituted or substitutedaromatic hydrocarbon group and an unsubstituted or substituted siliconcontaining group, a hydrogen atom or a single bond, provided that R¹ andR² may cooperate with each other to bond the two 5-membered rings shownin the formula and provided that neighboring groups of R¹ or R² maycooperate with each other to form a cyclic structure; each of a and bindependently is an integer of 1 to 4; X represents a halogen atom or ahydrocarbon group optionally having at least one of hydrogen atomsthereof substituted with a halogen atom; and n is 0 or an integersubtractizig 2 from the valence of metal M.
 2. The bulk polymerizationcatalyst as claimed in claim 1, wherein the organometallic compoundrepresented by the formula (I) and the thiol are used in a molar ratioof 10:1 to 1:10,000.